Pen-Type Drug Injection Device and Optical Dose Value Decoding Systme with Additional Sensor to Distinguish Between Dose Dialling and Dose Delivery Mode

ABSTRACT

An optical decoding system comprising: a first optical sensor configured to be directed at a first rotatable component of a drug delivery device; a second optical sensor configured to be directed at a second rotatable component of a drug delivery device; and a processor configured to: receive signals from the first optical sensor, wherein the signals from the first optical sensor represent encoded dosage values present on the first rotatable component; receive signals from the second optical sensor, wherein the signals from the second optical sensor represent whether the second rotatable component is rotating or not; and to determine from the received signals whether the drug delivery device is in a drug dose dialling mode or a drug dose delivery mode.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a U.S. National Phase Application pursuant to35 U.S.C. §371 of International Application No. PCT/EP2014/050467 filedJan. 13, 2014, which claims priority to European Patent Application No.13151370.7 filed Jan. 15, 2013. The entire disclosure contents of theseapplications are herewith incorporated by reference into the presentapplication.

FIELD OF INVENTION

The present invention relates to an optical decoding system for a drugdelivery device.

BACKGROUND

Pen type drug delivery devices have application where regular injectionby persons without formal medical training occurs. This is increasinglycommon among patients having diabetes where self-treatment enables suchpatients to conduct effective management of their diabetes.

For good or perfect glycemic control, the dose of insulin or insulinglargine has to be adjusted for each individual in accordance with ablood glucose level to be achieved. The present invention relates tooptical decoding systems for injectors, for example hand-held injectors,especially pen-type injectors, that is to injectors of the kind thatprovide for administration by injection of medicinal products from amultidose cartridge.

A user undertaking self-administration of insulin will commonly need toadminister between 1 and 80 International Units. A user is also requiredto record their dosage history. The dosage history is an importantfactor in calculating future doses.

SUMMARY

A first aspect of the invention provides an optical decoding systemcomprising:

a first optical sensor configured to be directed at a first rotatablecomponent of a drug delivery device;

a second optical sensor configured to be directed at a second rotatablecomponent of a drug delivery device; and

a processor configured to receive signals from the first and secondoptical sensors and to determine a mode of operation of the drugdelivery device from the received signals.

The current mode of operation of the drug delivery device can then becommunicated to a user of the device. The user does not have todetermine the mode themselves.

Being able to determine the mode of operation of the drug deliverydevice is advantageous, as the dose of medicament which has beendelivered can be determined. It is important to accurately record thedose of medicament which has actually been delivered in order toaccurately assess the effect of the medicament on the user's health andfor the calculation of future medicament doses.

The first rotatable component may be arranged to rotate and translaterelative to the first optical sensor when the drug delivery device is ina first mode and in a second mode, while the second rotatable componentmay be arranged to rotate and translate relative to the second opticalsensor when the drug delivery device is in the first mode and only totranslate when the drug delivery device is in the second mode. Thedifference in movement between the first and second rotatable componentsallows the operational mode of the device to be determined.

The first mode may be a drug dose dialling mode and the second mode maybe a drug dose delivery mode.

The processor may be further configured to determine a drug dose thathas been delivered and to cause a record of the delivered dose to bestored in a memory. The processor may be configured to determine thedrug dose that has been delivered using signals received from the firstoptical sensor. This allows the delivered dose to be calculatedautomatically and accurately. It is often necessary for a user of such adrug delivery device to adjust the medicament dose based at least inpart on their previous doses. It is therefore advantageous to accuratelyand automatically record all dispensed doses.

The optical decoding system may further comprise a display device andthe processor may be configured to cause the display device to displayan indication of the drug dose that has been delivered.

The optical decoding system may further comprise one or more LEDsconfigured to illuminate portions of the first and/or second rotatablecomponents. The reliability and sensitivity of images captured by thefirst and/or second optical sensors may be improved if the rotatablecomponents are illuminated.

The optical decoding system may further comprise a switch and a changein the state of the switch may be configured to cause the first andsecond optical sensors to be activated. The drug delivery device andswitch may be configured to be arranged such that the state of theswitch changes when the drug delivery device moves from a zero unit drugdose arrangement to a single unit drug dose arrangement. Activating thefirst and second sensors only when a change in the state of a switch isdetected results in power savings compared to powering the sensorswhenever the drug delivery device is on.

A second aspect of the invention provides a drug delivery devicecomprising a housing retaining the optical decoding system of the firstaspect of the invention. The drug delivery device may comprise the firstrotatable component and the second rotatable component. Integrating theoptical decoding system with the drug delivery device increases theutility of that device.

In a third aspect of the invention, the optical decoding system of thefirst aspect may be part of a supplementary device configured to beattached to the drug delivery device. Implementing the optical decodingsystem in a supplementary device allows the optical decoding system tobe applied to devices without an electronic monitoring capability, orwith a less sophisticated monitoring capability.

A fourth aspect of the invention provides a method of determining a modeof operation of a drug delivery device comprising:

receiving a signal from a first optical sensor directed at a firstrotatable component of the drug delivery device;

receiving a signal from a second optical sensor directed at a secondrotatable component of the drug delivery device; and

determining that the drug delivery device is in a first mode ofoperation if the second rotatable component is rotating when the firstrotatable component is rotating or determining that the drug deliverydevice is in a second mode of operation if the second rotatablecomponent is not rotating when the first rotatable component isrotating.

Being able to determine the mode of operation of the drug deliverydevice is advantageous, as the dose of medicament which has beendelivered can be determined. It is important to accurately record thedose of medicament which has actually been delivered in order toaccurately assess the effect of the medicament on the user's health andfor the calculation of future medicament doses. The difference inmovement between the first and second rotatable components allows theoperational mode of the device to be determined.

The first mode of operation may be a drug dose dialling mode and thesecond mode of operation may be a drug dose delivery mode.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 a shows an external view of a drug delivery device suitable forimplementing the present invention;

FIG. 1 b shows an internal view of the drug delivery device of FIG. 1 a;

FIG. 2 shows a schematic diagram of some of the electronic componentssuitable for implementing the present invention;

FIG. 3 is a cross-section showing detail of a dose setting mechanism ofa drug delivery device according to embodiments of the invention;

FIG. 4 shows an optically encoded sleeve suitable for use with theinvention;

FIG. 5 shows a 81 position optical code suitable for use with theinvention;

FIG. 6 shows an optically encoded dial suitable for use with theinvention;

FIG. 7 shows the proximal end of a different drug delivery device inwhich the invention may be used; and

FIG. 8 is a cross-section through the dose setting mechanism of a drugdelivery device showing an additional switch.

DETAILED DESCRIPTION

Referring firstly to FIGS. 1 a and 1 b, an external view and an internalview of a drug delivery device 100 according to embodiments of theinvention are shown. The device 100 shown in FIGS. 1 a and 1 b is a pentype injection device, having an elongate cylindrical shape, for settingand delivering a medicament, such as insulin. The device 100 comprises ahousing 102 having a first housing part 104 and a second housing part106. A rotatable dial 108 is located at a first (or proximal) end of thefirst housing part 104. The rotatable dial 108 has substantially thesame outer diameter as the first housing part 104. The second housingpart 106 may be detachably connected to the second end of the firsthousing part 104. The second housing part 106 is configured to have aneedle (not shown) or similar drug delivery apparatus attached to it. Toachieve this, the second (or distal) end of the second housing part 106may have a threaded portion 110. The threaded portion 110 may have asmaller diameter than the remainder of the second housing part 106.

A display window 112 is located on the first housing part 104. A displaymay be disposed underneath the display window 112. The display may be anLCD display, a segmented display or any other suitable type of display.The display window 112 may cover a recess 114 in the first housingportion 104. As well as a display, a number of electronic components,described in greater detail with reference to FIG. 2, may be disposedunderneath the display window 112.

The first housing part 104 contains a drug dose setting and deliverymechanism. The second housing part 106 contains a drug cartridge 116.The drug contained in the drug cartridge 116 may be a medicament of anykind and may preferably be in a liquid form. The drug delivery mechanismof the first housing part 104 may be configured to engage with the drugcartridge 116 of the second housing part 106 to facilitate expulsion ofthe drug. The second housing part 106 may be detached from the firsthousing part 104 in order to insert a drug cartridge 116 or to remove aused cartridge. The first and second housing parts 104, 106 may beconnected together in any suitable way, for example with a screw orbayonet type connection. The first and second housing parts 104, 106 maybe non-reversibly connected together is such a way as the drug cartridge116 is permanently contained with the drug delivery device 100. Furtherthe first and second housing parts 104, 106 may form part of a singlehousing part.

The rotatable dial 108 is configured to be rotated by hand by a user ofthe drug delivery device 100 in order to set a drug dose to bedelivered. The dial 108 is connected to an internal threading systemwhich causes the dial 108 to be displaced axially from the housing 102as it is rotated in a first direction. The device 100 is configured,once a drug dose has been set by rotation of the rotatable dial 108, todeliver the set drug dose when a user exerts an axial force at theproximal end of the device. In some injection pen devices, the rotatabledial 108 may support a button (not shown) which must be depressed inorder to deliver the set drug dose.

Referring now to FIG. 2, a schematic diagram of electrical circuitry 200suitable for implementing the present invention is shown. The circuitry200 comprises a microprocessor 202, a non-volatile memory such as a ROM204, a writable non-volatile memory such as flash memory 205, a volatilememory such as a RAM 206, a display 210, a first optical sensor 212, asecond optical sensor 214, LEDs 216 and a bus 208 connecting each ofthese components. The circuitry 200 also comprises batteries 218 or someother suitable source of power for providing power to each of thecomponents.

The circuitry 200 may be integral with the device 100. Alternatively,the circuitry 200 may be contained within an electronic module that canbe attached to the device 100. In addition, the circuitry 200 maycomprise additional sensors, such as an optical character recognition(OCR) system or acoustical sensors.

The ROM 204 may be configured to store software and/or firmware. Thissoftware/firmware may control operations of the microprocessor 202. Themicroprocessor 202 utilises RAM 206 to execute the software/firmwarestored in the ROM to control operation of the display 210. As such themicroprocessor 202 may also comprise a display driver. The processor 202utilises the flash memory 205 to store determined amounts of dosedialled and/or determined amounts of dose dispensed, as will bedescribed in more detail below.

The batteries 218 may provide power for each of the components includingthe first and second optical sensors 212, 214 and LEDs 216. The supplyof power to the first and second optical sensors 212, 214 and LEDs 216may be controlled by the microprocessor 202. The microprocessor 202 mayreceive signals from the first and second optical sensors 212, 214 andis configured to interpret these signals. Information may be provided onthe display 210 at suitable times by operation of the software/firmwareand the microprocessor 202. This information may include measurementsdetermined from the signals received by the microprocessor 202 from thefirst and second optical sensors 212, 214 such as the drug dose whichhas been set and/or delivered. The display 210 may also show additionalinformation, such as the actual time, the time of the lastusage/injection, a remaining battery capacity, one or more warningsigns, and/or the like.

The first and second optical sensors 212, 214 may be configured tocapture pixelated greyscale images of printed images or patterns whichoptically encode information. The images or patterns may be printed onmovable parts of the drug delivery device 100 which the first and secondoptical sensors 212, 214 are configured to be directed at. The one ormore LEDs 216 are also directed at the printed images/patterns in orderto provide illumination for the sensors 212, 214. For example, the firstand second optical sensors 212, 214 may detect the intensity pattern oflight reflected from the printed images/patterns. The LEDs 216 andsensors 212, 214 may be configured to operate at various wavelengths oflight. The LEDs 216 and sensors 212, 214 may, for example, operate ininfra-red. Each of the first and second optical sensors 212, 214 mayhave an integral LED 216, or the LEDs 216 and sensors 212, 214 maycomprise separate units. Software stored in the ROM 204 allows themicroprocessor 202 to determine from the signals received from the firstand second optical sensors 212, 214 whether first and second rotatablecomponents are rotating. Software also allows the microprocessor 202 toanalyse and decode images received from the first and second opticalsensors 212, 214 and to determine a rotational position of each of thefirst and second rotatable components.

The circuitry 200 may comprise further components which are not shown.For example, the circuitry 200 may comprise one or more user inputs inthe form of hardware or software keys. The circuitry 200 may comprise aspeaker and/or a microphone. The circuitry 200 may also comprise one ormore means of removing or communicating information stored in the ROM204 or flash memory 205, such as a wireless transceiver, a card slot ora cable port (e.g. a USB port).

FIG. 3 is a cross-sectional view of a part of a dose setting mechanismof a drug delivery device 100. A detailed example of the operation of adose setting and delivery mechanism supported within the first housingpart 104 can be found in published PCT application WO2010/139640, whichis incorporated herein by reference. This document gives details of oneparticular drug delivery device mechanism. However, the invention may beimplemented in a wide variety of different drug delivery devices havingdifferent mechanisms.

Referring now to FIG. 3, the first housing part 104 comprises an outerhousing 300, an inner housing 306 and an encoded number sleeve 302.These components are hollow cylinders arranged concentrically. Theencoded number sleeve 302 is disposed between the inner and outerhousings 306, 300. The rotatable dial 108 is located at the proximal endof the outer housing 300. Integral with the rotatable dial 108 is adialling sleeve 304. The dialling sleeve 304 comprises a hollow cylinderdisposed between the outer housing 300 and the encoded number sleeve302.

A recess 114 is provided in the outer housing 300. Electronic componentsincluding the display 210 may be received in the recess 114. The firstoptical sensor 212 (also referred to herein as the number sleeve sensor212) is shown schematically at the position of the recess 114. Thenumber sleeve sensor 212 may be part of the electronic module receivedin the recess 114, or alternatively may be part of an external deviceconfigured to be attached to the drug delivery device 100. The secondoptical sensor 214 (also referred to herein as the dialling sleevesensor 214) is shown schematically disposed at the proximal end of theouter housing 300. The dialling sleeve sensor 214 may be an integralpart of the drug delivery device 100. For example, the dialling sleevesensor may be received in a secondary recess (not shown) or the outerhousing 300. Alternatively, the dialling sleeve sensor 214 may be partof an external device configured to be attached to the drug deliverydevice 100. In either case, when in use the dialling sleeve sensor 214is arranged to be directed at an outer surface of the dialling sleeve304.

As can be seen in FIG. 3, the outer diameter of the encoded numbersleeve 302 may be reduced towards the proximal end of the first housingpart 104 in order to provide a space for the dialling sleeve 304. Thethickness of the outer housing 300 may also be reduced at the proximalend to provide this space. The dialling sleeve 304 extends into thefirst housing part 104 no further than the recess 114 such that when thefirst optical sensor 212 is positioned at or in the recess 114 it isdirected at the encoded number sleeve 302, while the second opticalsensor 214 is directed at the dialling sleeve 304.

The inner housing 306 has a thread 308 provided on a part of its outersurface. The encoded number sleeve 302 has a corresponding threaddisposed on a part of its inner surface. The inner housing 306 is fixedrelative to the outer housing 300. Therefore the threaded engagementbetween the inner housing 306 and the number sleeve 302 causes thenumber sleeve to move axially relative to the outer housing 300 whenrotated (and vice versa). In an initial configuration (shown in FIG. 3),the rotatable dial 108 is coupled to the encoded number sleeve 302. Thiscoupling may be provided by a toothed engagement at the proximal end ofthe encoded number sleeve 302. However, the skilled person will be awareof other methods by which these components may be coupled. The dial 108and the encoded number sleeve 302 may be coupled via a third rotatablecomponent. Thus when the rotatable dial 108 is rotated, the encodednumber sleeve 302 also rotates. This causes the rotatable dial 108 andall components coupled thereto to move axially out of the first housingpart 104. If the dial 108 is rotated in the opposite direction, it movesback into the first housing part 104.

After a dose has been dialled into the drug delivery device 100 it maybe dispensed by applying an axial load to the distal end of therotatable dial 108. The rotatable dial 108 and integral dialling sleeve304 are able to move axially relative to the encoded number sleeve 302when this axial load is applied. Biasing means (not shown) may beprovided to bias the rotatable dial 108 and the number sleeve 302 apart,i.e. to bias the rotatable dial 108 in the distal direction relative tothe number sleeve 302. This position is shown in FIG. 3. When a forcesufficient to overcome the bias is applied, the rotatable dial movesaxially so that the proximal end of the number sleeve 302 enters thespace 312 internal to the rotatable dial 108. This relative axialmovement between the rotatable dial and the number sleeve 302 causesthese components to be decoupled. For example, the toothed engagement atthe proximal end of the encoded number sleeve 302 may be disengaged or aclutch formed by a different part of the mechanism may be disengaged.

When all of the allowed relative movement between the rotatable dial 108and number sleeve 302 has occurred, the axial load on the rotatable dial108 is transferred to other components of the mechanism. The axial forceis transferred to a spindle 314, disposed centrally within themechanism, via a drive sleeve 316 in order to cause expulsion of amedicament from the drug cartridge 116. The axial force is alsotransferred to the encoded number sleeve 302 which moves axially backinto the first housing part 104. Due to the threaded connection of theencoded number sleeve 302 with the inner housing 306, the number sleeverotates as it moves axially back into the first housing part 104. As therotatable dial 108 and integral dialling sleeve 304 are decoupled fromthe number sleeve 302 and coupled, via the drive sleeve 316, to theinner housing 306, they do not rotate as they move axially back into thefirst housing part 104.

FIG. 4 shows a perspective view of the encoded number sleeve 302 removedfrom the drug delivery device 100. The outer surface of the numbersleeve 302 has a helical track 400 comprising a sequence of images. Eachof the images encodes information and is designed to be viewed by thenumber sleeve sensor 212. The drug delivery device 100 may be configuredto deliver a maximum of 80 units of medicament. The track 400 maytherefore comprise a series of 81 encoded images encoding positions 0 to80. FIG. 5 is a table showing an encoded image scheme which may be usedin the present invention. Each of the images in this scheme is comprisedof a number of data bits which may be coloured black or white. Theimages are repeated in the four quadrants of a square. This allows forthe compensation of manufacturing tolerances which may prevent a singleencoded image from being viewed fully by the number sleeve sensor 212.The scheme of FIG. 5 is merely one example of suitable encoded images.The encoded image scheme may instead comprise a series of dot matrixpatterns, a series of barcodes or similar or standard Arabic numeralsand may comprise a single image per position or multiple repeatedimages. The encoded images may be printed, marked, indented, etched orsimilar onto the track 400.

The encoded number sleeve 302 is arranged within the mechanism such thatwhen no dose is dialled into the drug delivery device 100 the firstencoded image (encoding position “0”) is located directly underneath therecess 114. This allows the encoded image to be viewed by the firstoptical sensor 212. The pitch of the track 400 is the same as thethreads on the encoded number sleeve 302 and inner housing 306 such thatas the number sleeve 302 rotates and moves axially out of the firsthousing part 104 the track 400 remains located underneath the recess 114in the outer housing 300. The first optical sensor 212 is configured tocapture the images and to relay signals to the microprocessor 202. Oneor more LEDs 216 may illuminate the track 400 to allow the first opticalsensor 212 to capture images. The microprocessor 202 is configured toemploy software stored in the ROM 204 to determine the content of eachimage, for example which parts of the image are black and which partsare white, and to identify a corresponding rotational position of theencoded number sleeve 302 relative to the sensor 212. The microprocessor202 may achieve this by consulting a table stored in the ROM 204 whichrelates the content of each image to a rotational position of the numbersleeve 302 and hence to a drug dose which has been dialled.

FIG. 6 is a plan view of the dialling sleeve 304 removed from the drugdelivery device 100. The dialling sleeve 304 may be formed integrallywith the rotatable dial 108, or maybe fixed to the rotatable dial 108.An incremental optical code is marked on an outer surface of thedialling sleeve 304. In the illustrated embodiment, the incremental codecomprises alternating black bands 600 and white bands 602 extendingaxially. In some embodiments, the black bands 600 may be printed ontothe dialling sleeve 304, which is white. In some other embodiments, thewhite bands 602 may also be printed. Any markings which allow rotationof the dialling sleeve 304 to be detected by the second optical sensor214 may be used, such as a series of equally spaced marks. The surfaceof the dialling sleeve 304 may be a smooth cylinder, or may becorrugated. The corrugations may form the incremental markings Thedialling sleeve 304 may have a textured surface with well definedparameters allowing rotation of the dialling sleeve 304 to be detected.

Exemplary operation of the drug delivery device 100 will now bedescribed. To dial a dose, a user grasps and twists the rotatable dial108. The rotatable dial 108 is coupled to the encoded number sleeve 302,which therefore also rotates. The threaded connection between theencoded number sleeve 302 and the inner housing 306 causes the numbersleeve 302 and dialling sleeve 304 to move axially out of the firsthousing part 104. The movement of the encoded number sleeve 302 anddialling sleeve 304 describes a helix.

As the number sleeve 302 moves helically, it is viewed by the firstoptical sensor 212. In some embodiments, the first optical sensor 212 ispart of an electronics module received in the recess 114 in the outerhousing 300. In other embodiments, the first optical sensor 212 isinstalled on the inner surface of the outer housing 300 duringmanufacture. The first optical sensor 212 may be connected to the otherelectronic components via conductive tracks running along and/or throughthe outer housing 300. In some other embodiments, the first opticalsensor 212 is part of a supplemental device configured to be releasablyattached to the drug delivery device 100. The first optical sensor 212is configured to be directed at the encoded number sleeve 302 so as toview the encoded images of the track 400. One or more LEDs 216 areconfigured to illuminate the track 400. Images may be captured by thefirst optical sensor 212 at periodic intervals, for example twice persecond. The images captured by the first optical sensor 212 are relayedto the microprocessor 202 for decoding.

As the dialling sleeve 304 moves helically, it is viewed by the secondoptical sensor 214. One or more LEDs 216 are configured to illuminatethe surface of the dialling sleeve 304. The second optical sensor 214observes alternating black and white stripes as the dialling sleeve 304rotates. The second optical sensor 214 may capture images atpredetermined intervals. The interval may be the same as or different tothat of the first optical sensor 212. The images captured by the secondoptical sensor 214 are relayed to the microprocessor 202 for analysis.As the second optical sensor 214 is separated from the otherelectronics, conductive tracks may pass through the outer housing 300 orbe printed onto an inner surface of the outer housing 300 to transmitsignals to and from the sensor 214.

The angular width of the black and white bands 600, 602 ispredetermined. For example, the surface of the dialling sleeve 304 maycomprise 12 white bands 602 and 12 black bands 600. The microprocessor202 can therefore use the received image signals to determineincrementally the amount of rotation (in either direction) of thedialling sleeve 304.

The field of view of each of the first and second optical sensors 212,214 may be different. The field of view of the first optical sensor 212must be large enough to encompass the whole of each encoded image inorder for the image to be successfully decoded. The second opticalsensor 214 only needs to determine whether the dialling sleeve 304 isrotating or not, so the field of view should preferably be no wider thanthe width of the black and white bands 600, 602.

As previously mentioned, the optical decoding system described herein issuitable for use with a wide range of different drug delivery devices.By way of further example, FIG. 7 shows the proximal end of a differentdrug delivery device 700 in which the invention may be used. FIG. 7shows both an end view (left) and a plan view (right) of the proximalend of the drug delivery device 700.

The device 700 comprises the same first and second housing parts 104,106, with the first housing part 104 containing the drug dose settingand delivery mechanism and the second housing part (not visible in FIG.7) containing a drug cartridge. The device 700 also has a rotatable dial702 (also referred to herein as a dose selector) similar or identical tothat previously described.

The drug dose setting and delivery mechanism of the device 700 shown inFIG. 7 is constructed such that when the rotatable dial 702 is rotatedto set a dose, it does not move axially out of the housing 104, but onlyrotates. This may be achieved by providing a drive spring which storesenergy when the rotatable dial 702 is rotated. A cylindricalcompression/tension or torsion spring is suitable for this purpose as itcan be easily incorporated into the cylindrical body of the device 700.

After a dose has been dialled into the drug delivery device 700 it maybe dispensed by applying an axial load to the distal end of therotatable dial 702. The rotatable dial 702 may house a dose deliverybutton which is depressed in order to dispense a dose, or alternativelythe whole rotatable dial 702 may be depressed axially in order todispense a dose. The drug delivery device 700 also has a clutchmechanism which disengages the rotatable dial 702 from the drive springwhen this axial load is applied allowing the drive spring to return toits original position without rotation of the rotatable dial 702. Inreturning to its original position, the drive spring forces a spindle toadvance into the drug cartridge and thereby cause expulsion of amedicament from the drug cartridge.

In these embodiments, the encoded number sleeve (not visible in FIG. 7)is in mechanical communication with the drive spring and moves axiallywhen energy is stored in or released from the drive spring. The encodednumber sleeve moves in a first longitudinal direction when a dose isdialed into the drug delivery device 700 and in a second (opposite)longitudinal direction when a dose is dialed out of the drug deliverydevice 700 or when a dose is dispensed form the drug delivery device700. The encoded number sleeve need not be a hollow cylinder as in thepreviously described embodiments, as it does not rotate, but only moveslongitudinally. Thus the encoded images or numbers are printed in alongitudinal line on the encoded number sleeve such that they passthrough the field of view of the first optical sensor 212.

In the embodiments represented by FIG. 7, the drug delivery device 700also comprises a sensor arm 704 which extends from the first housingpart 104 such that it is adjacent to the rotatable dial 702. The secondoptical sensor 214 is housed within this sensor arm 704 and directed atthe rotatable dial 702. Alternatively, the sensor arm 704 and secondoptical sensor 214 may be part of an external device configured to beattached to the drug delivery device 100.

The second optical sensor 214 is configured to observe the rotation ofthe rotatable dial 702 directly. This removes the need to have a secondwindow allowing the dialing sleeve to be visible to the second opticalsensor 214 and the need for any modification of the dialing sleeve. Therotatable dial 702 has a corrugated surface to aid in gripping andturning the dial. The corrugations on the rotatable dial 702 may becoloured or shaded to allow the second optical sensor 214 to detectrotation of the dial 702. The angular width of the corrugations may beknown, such that the amount of rotation can also be determined form thesignals produced by the second optical sensor 214. However, in mostembodiments it is only required that the second optical sensor 214detect whether the rotatable dial 702 is rotating or stationary.Alternatively, the second optical sensor 214 may be replaced by anothertype of sensor, for example a proximity sensor which detects the changesin surface height of the dial 702 or a capacitive or hall sensor.

In use, a user grasps and twists the rotatable dial 702 to set a dose.The rotatable dial 702 rotates, but does not move axially. The rotatabledial 702 is coupled to a drive spring which stores energy as the dial isrotated. This in turn also causes the encoded number sleeve to move in afirst longitudinal direction. As the number sleeve moves longitudinally,it is viewed by the first optical sensor 212. In some embodiments, thefirst optical sensor 212 is part of an electronics module received inthe recess 114 in the first housing part 104. In other embodiments, thefirst optical sensor 212 is installed on the inner surface of the firsthousing part 104 during manufacture. The first optical sensor 212 may beconnected to the other electronic components via conductive tracksrunning along and/or through the housing. In some other embodiments, thefirst optical sensor 212 is part of a supplemental device configured tobe releasably attached to the drug delivery device 700.

As the rotatable dial 702 moves longitudinally, it is viewed by thesecond optical sensor 214. One or more LEDs 216 may be provided andconfigured to illuminate the surface of the rotatable dial 702.Alternatively, the second optical sensor 214 may rely on ambient lightor may be another type of sensor as previously described. In someembodiments, the corrugations of the rotatable dial 702 form alternatingblack and white bands. The second optical sensor 214 observes thesealternating black and white bands as the rotatable dial 702 rotates. Thesecond optical sensor 214 may capture images at predetermined intervals.The interval may be the same as or different to that of the firstoptical sensor 212. The images captured by the second optical sensor 214are relayed to the microprocessor 202 for analysis. Conductive tracksmay pass through the housing or be printed onto an inner surface of thehousing to transmit signals to and from the sensor 214.

The processor 202 receives signals from the first and second sensors212, 214 and determines whether the drug delivery device 700 is in adrug dose dialling mode or a drug dose delivery mode. The processor mayuse the signals from the sensor to distinguish three differentsituations.

1) If the first optical sensor 212 detects movement of the number sleevein a first longitudinal direction (e.g. towards the rotatable dial) andthe second optical sensor 214 detects rotation of the rotatable dial702, then the processor 202 determines that the drug delivery device 700is in a drug dose dialling mode and that a dose is being dialled intothe device.

2) If the first optical sensor 212 detects movement of the number sleevein a second (opposite) longitudinal direction (e.g. towards the needle)and the second optical sensor 214 detects rotation of the rotatable dial702, then the processor 202 determines that the drug delivery device 700is in a drug dose dialling mode and that a dose is being dialled out ofthe device. This could be for example a situation, wherein a usercorrects a too high dose that has been dialed into the device. Anotherexample could be that a user has decided to postpose application of themedicament and therefore is dialing out the previously dialled dose.

3) If the first optical sensor 212 detects movement of the number sleevein a second (opposite) longitudinal direction (e.g. towards the needle)and the second optical sensor 214 detects that the rotatable dial 702 isnot rotating, then the processor 202 determines that the drug deliverydevice 700 is in a drug dose delivery mode and that a dose is beingejected from the device.

Referring also to FIG. 8, an activation switch 800 is shown. Althoughthis feature is described with reference to the first type of drugdelivery device 100, it is equally applicable to the second type of drugdelivery device 700 described with reference to FIG. 7. The first andsecond optical sensors 212, 214 and LEDs 216 may be activated byrotation of the dial 108. This may be achieved by a switch 800 which istriggered whenever the dial 108 is rotated away from the zero doseposition. The switch 800 may be comprised of an electromechanical switchhaving a protrusion 802. The protrusion 802 may be biased towards aprotruding position. The protrusion 802 passes through a recess in theouter body 300, which may be part of the recess 114. The proximal end ofthe dialling sleeve 304 may be configured to contact the protrusion 802when the drug delivery device 100 is in the zero dose position, as shownin FIG. 8. As the dial 108 is rotated away from the zero dose position,the dialling sleeve 304 moves axially. The protrusion 802 can then enterthe space left by the dialling sleeve 304. This movement changes thestate of the switch 800. In an alternative embodiment, the protrusion802 may contact the outer surface of the encoded number sleeve 302. Arecess may be cut into the outer surface of the encoded number sleeve302 and the protrusion enters this recess when the sleeve 302 is in thezero dose position. The recess and/or the protrusion 802 may have slopededges to allow the protrusion 802 to slide out of the recess when thesleeve 302 is rotated.

The state change of the switch 800 may be used as the trigger toactivate the first and second optical sensors 212, 214 and LEDs 216. Thedrug delivery device 100 (or supplemental device in some embodiments)may remain in a standby or sleep mode until the switch 800 changesstate. The first and second optical sensors 212, 214 and LEDs 216 arecomponents which consume power while active. Optical sensors may alsohave relatively high standby current requirements. The drug deliverydevice 100 (or supplemental device in some embodiments) is portable andthe batteries 218 have a limited capacity. The battery life of the drugdelivery device 100 is therefore conserved by activating thesecomponents only at the required time. The first and second opticalsensors 212, 214 and LEDs 216 may be deactivated when the drug deliverydevice 100 is returned to the zero dose position, or after apredetermined time delay after the delivery device 100 is returned tothe zero dose position.

Referring again to the first described drug delivery device 100,software stored in the ROM 204 also allows the microprocessor 202 to usethe signals received from the first and second optical sensors 212, 214to determine a mode of operation of the drug delivery device 100. Whenthe drug delivery device 100 is in a “dialling mode”, the dial 108 isrotated to dial a dose into or out of the device 100. This causes boththe encoded number sleeve 302 and dialling sleeve 304 to move helically,as previously described. The first optical sensor 212 views the encodedimages on the track 400 passing in sequence. Each of these imagesencodes a unique rotational position, allowing the currently dialleddose to be determined. The second optical sensor 214 views thealternating black and white bands 600, 602 as they rotate past. As bothsensors view helical motion, it is determined that the drug deliverydevice 100 is in a dialling mode. While the drug delivery device 100 isin the dialling mode, the output from the number sleeve sensor 212 canbe used by the microprocessor to determine the value of the currentdialled dose. This value can be displayed on the display 210.

When an axial load is applied to the rotatable dial 108, the drugdelivery device 100 is in a “dispensing mode”. The rotatable dial 108and dialling sleeve 304 are de-coupled from the encoded number sleeve302, as previously described. As the encoded number sleeve 302translates back into the first housing part 104, it moves in the samehelical way as in the dialling mode. However, the rotatable dial 108 anddialling sleeve 304 translate only and do not rotate. Therefore, duringdispensing, the first optical sensor 212 views the encoded images on thetrack 400 passing in sequence, but the second optical sensor 214 viewsno change in the incremental encoded images on the dialling sleeve 304and no change in the output of the second optical sensor 214 results.The microprocessor 202 can thus determine that the drug delivery device100 is in a dispensing mode. While the drug delivery device 100 is inthe dispensing mode, the output from the number sleeve sensor 212 can beused by the microprocessor to determine the value of an injected dose.This value can be displayed on the display 210 and stored in the flashmemory 205. Results of previous dispensing action may be later recalledfrom the flash memory 205 and displayed on the display 210.

Being able to determine the mode of operation of the drug deliverydevice 100 is advantageous, as the drug delivery device 100 (or theattached supplemental device) is able to calculate electronically thedose of medicament which has been delivered. For example, a user maydial in a dose but then dial some of the dose out before dispensing theremaining dose. Alternatively, a user may deliver only a part of a doseand may dial the remaining dose out. It is important to accuratelyrecord the dose of medicament which has actually been delivered in orderto accurately assess the effect of the medicament on the user's healthand for the calculation of future medicament doses.

1-13. (canceled)
 14. An optical decoding system comprising: a firstoptical sensor configured to be directed at a first rotatable componentof a drug delivery device; a second optical sensor configured to bedirected at a second rotatable component of a drug delivery device; anda processor configured to: receive signals from the first opticalsensor, wherein the signals from the first optical sensor representencoded dosage values present on the first rotatable component; receivesignals from the second optical sensor, wherein the signals from thesecond optical sensor represent whether the second rotatable componentis rotating or not; and to determine from the received signals whetherthe drug delivery device is in a drug dose dialling mode or a drug dosedelivery mode.
 15. An optical decoding system according to claim 14,wherein the processor is further configured to determine a drug dosethat has been delivered and to cause a record of the delivered dose tobe stored in a memory.
 16. An optical decoding system according to claim15, wherein the processor is configured to determine the drug dose thathas been delivered using signals received from the first optical sensor.17. An optical decoding system according to claim 15, wherein theoptical decoding system further comprises a display device and whereinthe processor is configured to cause the display device to display anindication of the drug dose that has been delivered.
 18. An opticaldecoding system according to claim 14, wherein the optical decodingsystem further comprises one or more LEDs configured to illuminateportions of the first and/or second rotatable components.
 19. An opticaldecoding system according to claim 14, wherein the optical decodingsystem further comprises a switch and wherein a change in the state ofthe switch is configured to cause the first and second optical sensorsto be activated.
 20. An optical decoding system according to claim 19,wherein the drug delivery device and switch are configured to bearranged such that the state of the switch changes when the drugdelivery device moves from a zero unit drug dose arrangement to a singleunit drug dose arrangement.
 21. A drug delivery device comprising ahousing retaining the optical decoding system of claim
 14. 22. A drugdelivery device according to claim 21, the drug delivery devicecomprising the first rotatable component and the second rotatablecomponent.
 23. A drug delivery device according to claim 21, wherein:the first rotatable component is arranged to rotate and translaterelative to the first optical sensor when the drug delivery device is ina drug dose dialling mode and in a drug dose delivery mode; and thesecond rotatable component is arranged to rotate and translate relativeto the second optical sensor when the drug delivery device is in thedrug dose dialling mode and only to translate when the drug deliverydevice is in the drug dose delivery mode.
 24. A drug delivery deviceaccording to claim 21, wherein: the first rotatable component isarranged to translate relative to the first optical sensor when the drugdelivery device is in a drug dose dialling mode and in a drug dosedelivery mode; and the second rotatable component is arranged to rotaterelative to the second optical sensor when the drug delivery device isin the drug dose dialling mode and to remain stationary when the drugdelivery device is in the drug dose delivery mode.
 25. An opticaldecoding system according to claim 14, wherein the optical decodingsystem is part of a supplementary device configured to be attached tothe drug delivery device.
 26. A method of determining a mode ofoperation of a drug delivery device comprising: receiving a signal froma first optical sensor directed at a first rotatable component of thedrug delivery device, wherein the signal from the first optical sensorrepresents encoded dosage values present on the first rotatablecomponent; receiving a signal from a second optical sensor directed at asecond rotatable component of the drug delivery device, wherein thesignals from the second optical sensor represent whether the secondrotatable component is rotating or not; and determining that the drugdelivery device is in a drug dose dialling mode of operation if thesecond rotatable component is rotating when the first rotatablecomponent is rotating or determining that the drug delivery device is ina drug dose delivery mode of operation if the second rotatable componentis not rotating when the first rotatable component is rotating.